Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on Recurring Basis

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2017 and 2016 and by level within the fair value hierarchy:

Fair value measurement as of December 31, 2017:

			Quoted prices in		Significant other		Significant
Financial assets			active markets for		observable		unobservable
			identical assets		inputs		inputs
Type of Instrument	Total		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents:
Money market fund and checking accounts	$	9,388	$	9,388	$	—	$	—
Available-for-sale marketable securities:
Money market fund		39,951		—		39,951		—
U.S. government agency obligations		7,794		—		7,794		—
Corporate bonds		15,907		—		15,907		—
Commercial paper		19,529		—		19,529		—
Restricted cash:
Commercial money market account		769		769		—		—
Total financial assets	$	93,338	$	10,157	$	83,181	$	—

Fair value measurement as of December 31, 2016:

			Quoted pricesin		Significant other		Significant
Financial assets			active markets for		observable		unobservable
			identical assets		inputs		inputs
Type of Instrument	Total		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents:
Money market fund and checking accounts	$	12,092	$	12,092	$	—	$	—
Available-for-sale marketable securities:
Money market fund		8,276		—		8,276		—
U.S. Treasury securities		2,522		—		2,522		—
U.S. government agency obligations		3,502		—		3,502		—
Corporate bonds		16,677		—		16,677		—
Commercial paper		15,207		—		15,207		—
Restricted cash:
Commercial money market account		1,469		1,469		—		—
Total financial assets	$	59,745	$	13,561	$	46,184	$	—